[PATCHv10 0/6] lib/rwmmio/arm64: Add support to trace register reads/writes
Sai Prakash Ranjan
quic_saipraka at quicinc.com
Wed Apr 20 19:00:19 PDT 2022
Hi Arnd,
On 4/8/2022 4:47 PM, Sai Prakash Ranjan wrote:
> Hi Arnd,
>
> On 2/24/2022 11:37 AM, Sai Prakash Ranjan wrote:
>> Generic MMIO read/write i.e., __raw_{read,write}{b,l,w,q} accessors
>> are typically used to read/write from/to memory mapped registers
>> and can cause hangs or some undefined behaviour in following cases,
>>
>> * If the access to the register space is unclocked, for example: if
>> there is an access to multimedia(MM) block registers without MM
>> clocks.
>>
>> * If the register space is protected and not set to be accessible from
>> non-secure world, for example: only EL3 (EL: Exception level) access
>> is allowed and any EL2/EL1 access is forbidden.
>>
>> * If xPU(memory/register protection units) is controlling access to
>> certain memory/register space for specific clients.
>>
>> and more...
>>
>> Such cases usually results in instant reboot/SErrors/NOC or interconnect
>> hangs and tracing these register accesses can be very helpful to debug
>> such issues during initial development stages and also in later stages.
>>
>> So use ftrace trace events to log such MMIO register accesses which
>> provides rich feature set such as early enablement of trace events,
>> filtering capability, dumping ftrace logs on console and many more.
>>
>> Sample output:
>>
>> rwmmio_write: __qcom_geni_serial_console_write+0x160/0x1e0 width=32 val=0xa0d5d addr=0xfffffbfffdbff700
>> rwmmio_post_write: __qcom_geni_serial_console_write+0x160/0x1e0 width=32 val=0xa0d5d addr=0xfffffbfffdbff700
>> rwmmio_read: qcom_geni_serial_poll_bit+0x94/0x138 width=32 addr=0xfffffbfffdbff610
>> rwmmio_post_read: qcom_geni_serial_poll_bit+0x94/0x138 width=32 val=0x0 addr=0xfffffbfffdbff610
>>
>> This series is a follow-up for the series [1] and a recent series [2] making use
>> of both.
>>
>> [1] https://lore.kernel.org/lkml/cover.1536430404.git.saiprakash.ranjan@codeaurora.org/
>> [2] https://lore.kernel.org/lkml/1604631386-178312-1-git-send-email-psodagud@codeaurora.org/
>>
>> Note in previous v4 version, Arnd suggested to benchmark and compare size with callback
>> based implementation, please see [3] for more details on that with brief comparison below.
>>
>>
>> **Inline version with CONFIG_FTRACE=y and CONFIG_TRACE_MMIO_ACCESS=y**
>> $ size vmlinux
>> text data bss dec hex filename
>> 23884219 14284468 532568 38701255 24e88c7 vmlinux
>>
>> **Callback version with CONFIG_FTRACE=y and CONFIG_TRACE_MMIO_ACCESS=y**
>> $ size vmlinux
>> text data bss dec hex filename
>> 24108179 14279596 532568 38920343 251e097 vmlinux
>>
>> $ ./scripts/bloat-o-meter inline-vmlinux callback-vmlinux
>> add/remove: 8/3 grow/shrink: 4889/89 up/down: 242244/-11564 (230680)
>> Total: Before=25812612, After=26043292, chg +0.89%
>>
>> [3] https://lore.kernel.org/lkml/466449a1-36da-aaa9-7e4f-477f36b52c9e@quicinc.com/
>>
>> Changes in v10:
>> * Use GENMASK(31, 0) for -Woverflow warning in irqchip tegra driver (Marc).
>> * Convert ETM4x ARM64 driver to use asm-generic IO memory barriers (Catalin).
>> * Collect ack from Catalin for arm64 change.
>>
>> Changes in v9:
>> * Use TRACE_EVENT_CLASS for rwmmio_write and post_write (Steven Rostedt).
>>
>> Changes in v8:
>> * Fix build error reported by kernel test robot.
>>
>> Changes in v7:
>> * Use lib/ instead of kernel/trace/ based on review comment by Steven Rostedt.
>>
>> Changes in v6:
>> * Implemented suggestions by Arnd Bergmann:
>> - Use arch independent IO barriers in arm64/asm
>> - Add ARCH_HAVE_TRACE_MMIO_ACCESS
>> - Add post read and post write logging support
>> - Remove tracepoint_active check
>> * Fix build error reported by kernel test robot.
>>
>> Changes in v5:
>> * Move arm64 to use asm-generic provided high level MMIO accessors (Arnd).
>> * Add inline logging for MMIO relaxed and non-relaxed accessors.
>> * Move nVHE KVM comment to makefile (Marc).
>> * Fix overflow warning due to switch to inline accessors instead of macro.
>> * Modify trace event field to include caller and parent details for more detailed logs.
>>
>> Changes in v4:
>> * Drop dynamic debug based filter support since that will be developed later with
>> the help from Steven (Ftrace maintainer).
>> * Drop value passed to writel as it is causing hangs when tracing is enabled.
>> * Code cleanup for trace event as suggested by Steven for earlier version.
>> * Fixed some build errors reported by 0-day bot.
>>
>> Changes in v3:
>> * Create a generic mmio header for instrumented version (Earlier suggested in [1]
>> by Will Deacon and recently [2] by Greg to have a generic version first).
>> * Add dynamic debug support to filter out traces which can be very useful for targeted
>> debugging specific to subsystems or drivers.
>> * Few modifications to the rwmmio trace event fields to include the mmio width and print
>> addresses in hex.
>> * Rewrote commit msg to explain some more about usecases.
>>
>> Prasad Sodagudi (1):
>> lib: Add register read/write tracing support
>>
>> Sai Prakash Ranjan (5):
>> arm64: io: Use asm-generic high level MMIO accessors
>> coresight: etm4x: Use asm-generic IO memory barriers
>> irqchip/tegra: Fix overflow implicit truncation warnings
>> drm/meson: Fix overflow implicit truncation warnings
>> asm-generic/io: Add logging support for MMIO accessors
>>
>> arch/Kconfig | 3 +
>> arch/arm64/Kconfig | 1 +
>> arch/arm64/include/asm/io.h | 41 ++------
>> arch/arm64/kvm/hyp/nvhe/Makefile | 7 +-
>> drivers/gpu/drm/meson/meson_viu.c | 22 ++---
>> .../coresight/coresight-etm4x-core.c | 8 +-
>> drivers/hwtracing/coresight/coresight-etm4x.h | 8 +-
>> drivers/irqchip/irq-tegra.c | 10 +-
>> include/asm-generic/io.h | 82 +++++++++++++++-
>> include/trace/events/rwmmio.h | 97 +++++++++++++++++++
>> lib/Kconfig | 7 ++
>> lib/Makefile | 2 +
>> lib/trace_readwrite.c | 47 +++++++++
>> 13 files changed, 273 insertions(+), 62 deletions(-)
>> create mode 100644 include/trace/events/rwmmio.h
>> create mode 100644 lib/trace_readwrite.c
>>
>>
>> base-commit: 754e0b0e35608ed5206d6a67a791563c631cec07
> Gentle ping, could you please take a look at this, would appreciate your reviews.
>
Gentle Ping !!
Thanks,
Sai
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